Iran has informed the United Nations that it last week warned Azerbaijan concerning "illegal activities" in the Alborz oil field in the Caspian Sea, reported the official Kuwaiti news agency, KUNA.

The Iranian Ministry of Foreign Affairs said in a letter to UN Secretary General Kofi Annan that it had passed the warning to Baku through its Tehran embassy, according to the agency.

Iran said that the Azeri state-owned oil corporation, in cooperation with foreign oil companies, intended to carry out activities in the field without the consent of Tehran.

Earlier this month, Iran rejected allegations by Azerbaijan that Iranian military aircraft made several incursions into Azeri airspace.

The Azeri news agency, Turan, reported that in the latest incident last Thursday, two Iranian fighter jets entered Azeri airspace for about 50 minutes, flying over an area about 180 kilometers south of Baku.

He said the aircraft had been on a routine patrol, adding that Tehran respected the borders of its Caspian neighbor.

Russian President Vladimir Putin has offered to mediate in the dispute between Iran and Azerbaijan over ownership of part of the oil-rich Caspian.

AFP had reported Moscow's concerns over an incident last month in which an Iranian warship threatened an Azeri oil-research vessel in the Caspian Sea.

The agency said that Iran's ambassador in Moscow, Mahdi Safari, was summoned to the Russian Foreign Ministry over the incident.

But an Iranian official said such reports were “baseless.”

Russia has urged Iran and Azerbaijan to act in a good-neighborly spirit, show wisdom and restraint and immediately start talks to resolve their dispute.

The incident that sparked the conflict took place when the Azeri geological survey vessel Geophysic-3 was reportedly approached on July 23 by an Iranian warship in Caspian waters about 150 kilometers (90 miles) south of Azerbaijan's capital, Baku.

Azeri President Heydar Aliyev, meanwhile, has been quoted by Reuters as saying that he would not allow a row with Iran over ownership of part of the Caspian to undermine relations between the neighbors – Albawaba.com